A tapered roller bearing comprises main components including: an inner ring having a raceway surface on its radially outer surface and further having a cone front face rib and a cone back face rib on axially opposite sides of the raceway surface; an outer ring having a raceway surface on its radially inner surface; a plurality of tapered rollers interposed between the raceway surfaces of the inner and outer rings; and a cage having pockets for containing and holding the tapered rollers. The cage includes: a small annular portion that is continuous on the small end face side of the tapered rollers; a large annular portion that is continuous on the large end face side of the tapered rollers; and a plurality of bars that connect the small and large annular portions. Each pocket is formed between adjacent ones of the bars and has a trapezoidal shape having a narrow side that receives the small diameter side of the tapered roller and a wide side that receives the large diameter side of the tapered roller.
Tapered roller bearings for supporting power transmission shafts of, for example, differentials and transmissions of automotive vehicles are used with their lower portions immersed in oil baths, and the oil in the oil baths that serves as a lubricating oil flows into the bearings as the bearings rotate. In a tapered roller bearing used for such applications, the lubricating oil flows from the small diameter side of the tapered rollers into the bearing. The lubricating oil flowing from the radially outer side of the cage flows along the raceway surface of the outer ring and passes therethrough toward the large diameter side of the tapered rollers. The lubricating oil flowing from the radially inner side of the cage flows along the raceway surface of the inner ring and passes therethrough toward the large diameter side of the tapered rollers.
In some of the tapered roller bearings used for parts into which the lubricating oil flows from the outside, cut-away portions are provided in each pocket of the cage such that the separate flows of the lubricating oil on the radially outer and inner sides of the cage pass through the respective cut-away portions. With such a configuration, the circulation of the lubricating oil in the bearings is improved (refer to Patent Documents 1 and 2). In the bearing described in Patent Document 1, cut-away portions 10d are provided in the central portions of bars 8 between pockets 9 of a cage 5, as shown in FIG. 21A, so that foreign substances contained in the lubricating oil are prevented from staying inside the bearing. In the bearing described in Patent Document 2, cut-away portions 10e are provided in a small annular portion 6 and a large annular portion 7 on axially opposite sides of each pocket 9 of a cage 5, as shown in FIG. 21B, so that the flow of the lubricating oil from the radially outer side of the cage toward the inner ring side is facilitated. Note that the dimensions of the pockets 9 in the drawings are the values used for Comparative Examples in a torque measurement test described later.
[Patent Document 1] Japanese Patent Application Laid-Open No. Hei 09-032858.
[Patent Document 2] Japanese Patent Application Laid-Open No. Hei 11-201149.
[Patent Document 3] Japanese Patent Application Laid-Open No. Hei 09-096352.
[Patent Document 4] Japanese Patent Application Laid-Open No. Hei 11-210765.